Preloaded bearing assemblies of the type mentioned are well known in the prior art and common. Often two tapered roller bearings (but, for example, also angular contact ball bearings, axial roller bearings, axial cylindrical roller bearings, axial ball bearings) are tensioned against each other axially in order to achieve a clearance-free supporting, for example, of a shaft in a housing.
Here the problem arises that with changes of the temperature of the machine assembly a corresponding thermal influence is also given on the bearing assembly, whereby the preload in the bearing assembly or the clearance in the same is disadvantageously changed.
An aspect of the disclosure is to further improve a bearing assembly of the above-mentioned type such that it is ensured that even with temperature changes the desired axial preload or a defined axial bearing clearance is maintained in the rolling-element bearings.
The solution of this object by the disclosure is characterized in that the second machine part includes a first conical abutment surface and that at least one of the rolling-element bearings includes a bearing ring that includes a second conical abutment surface, wherein an intermediate ring is disposed between the first conical abutment surface and the second conical abutment surface, which intermediate ring abuts on both conical abutment surfaces, wherein the bearing ring provided with the conical abutment surface as well as the second machine part is comprised of a metallic material at least in the region of its receiving of the bearing ring, and wherein the intermediate ring is comprised of a material that has a higher thermal expansion coefficient compared to the metallic material of the second machine part and of the bearing ring.
Here the intermediate ring is preferably comprised of a plastic, preferably of fluorinated rubber (available under the trade name “Viton”).
The two rolling-element bearings are preferably tapered roller bearings.
The cone angle of the first conical abutment surface preferably falls between 15° and 55°, particularly preferably between 15° and 30°. However, the cone angle of the second conical abutment surface preferably falls between 10° and 50°, particularly preferably between 10° and 25°.
The cone angle of the first conical abutment surface and the cone angle of the second conical abutment surface here can be the same size. However, it is also possible that the cone angle of the first conical abutment surface is greater than the cone angle of the second conical abutment surface.
The first and the second conical abutment surface here are in particular disposed in the same direction with respect to the axial direction.
According to one preferred exemplary embodiment of the disclosure the first conical abutment surface in the second machine part is formed by an abutment ring, which is disposed in the second machine part, wherein the abutment ring is comprised of a metallic material. For the purpose of reducing wear it is preferably provided in this case that means are available by which a rotation of the abutment ring about the axis of the bearing assembly relative to the bearing ring is prevented.
Using the proposed design of a bearing assembly it is achieved that even with a change of the temperature the adjustment or the clearance in two interacting rolling-element bearings can be held constant. This applies in particular with the use of two tapered roller bearings preloaded against each other.
Furthermore it is achieved by the above mentioned measures that wear of the components and in particular a “creeping” (i.e., a migrating of components relative to others) can be prevented or minimized
This is achieved by the use of materials that have a different thermal expansion. In the present case an intermediate ring made of plastic (in particular made of “Viton”) having a relatively large thermal expansion is preferably used, which is used with the components made of metal having a relatively small thermal expansion. The desired effect arises in interaction with the mentioned conical surfaces on which the intermediate ring abuts. The conical surfaces act as sliding surfaces, on which a sliding movement can take place if different thermally induced expansions arise. A precise axial movement of the intermediate ring relative to the outer ring of the one rolling-element bearing can thereby be generated, which serves for compensation of movements that take place with a thermal change.
The bearing rings and optionally also the housing as well as the abutment ring are usually comprised of steel or another metallic material having a similar thermal expansion coefficient. For orientation, it is mentioned that the thermal expansion coefficient here falls in the range of approximately 0.000011 to 0.000012 1/K (values of steel).
However, in plastics the thermal expansion coefficient falls significantly higher than in metals and usually falls above 0.000050 1/K.
An improvement of the adjustment of the two interacting rolling-element bearings thus advantageously arises via an axial clearance reduction.
The risk of “creeping” of the intermediate ring and thus the risk of increased wear is reduced or entirely prevented by an anti-creep ring, which is discussed above as means for preventing a rotation.
The cone angle of the two above-mentioned conical surfaces can be the same size or also chosen differently so that the radial thickness of the intermediate ring changes over the axial position of the same. With identical cone angles a constant radial thickness of the intermediate ring results. The choice of the respective cone angle results from the given or to-be-expected thermal conditions in the machine assembly.
The conical surfaces of the bearing ring or of the housing or of the abutment ring can be provided with a friction-reducing coating, wherein the friction-reducing coating is or includes in particular polytetrafluoroethylene (PTFE) or a sliding coating. The conical surfaces can also alternatively or additionally be provided with a lubricant.
The operation of the rolling-element bearing thus always takes place in the optimum preload range or bearing clearance range in order to achieve optimum operating conditions of the bearing (for example, a uniformly controllable heat development or a uniformly controllable rolling-element bearing load).
In the present case conical surfaces are discussed, which are formed in the bearing ring or in the housing or in the abutment ring. Of course it is also contained in the scope of the present disclosure when the surfaces in question are configured slightly crowned and then interact in the manner of two congruent spherical caps.
The disclosed solution can be used, for example, both in industrial transmissions and in automobile transmissions for automobiles and trucks (here also in differential transmissions). Tool spindle bearing assemblies are furthermore a preferred application.
An improved load distribution in an adjusted bearing assembly thus arises in an advantageous manner The present disclosure thus provides a compensating element that ensures that the bearing preload remains unchanged in the event of thermal changes.